Rotary electromagnetic actuator of cylindrical form

ABSTRACT

A rotary electromagnetic actuator comprises a coil having a core extending diametrically of a cylindrical casing. Parallel pole pieces of arcuate cross section extending forwardly from opposite ends of the core receive between their forward ends a rotor mounted on a shaft extending axially of the casing. A spring tends to rotate the rotor in one direction while an electromagnetic force rotates it in the opposite direction when the coil is energized. Stop pins limit the angular movement of the rotor.

United States Patent [191 Abel 451 July 3,1973

[ ROTARY ELECTROMAGNETIC ACTUATOR OF CYLINDRICAL FORM [75] Inventor: Donald J. Abel, I-Iicksville, NY.

[73] Assignee: Senson1cs,Inc., l-licksville, NY.

[22] Filed: Jan. 26, 1972 21 Appl. No.: 220,937

[52] US. Cl. 335/272, 335/281 [51] Int. Cl. H01f 7/14 [58] Field of Search 335/270, 272, 279, 335/281 [56] References Cited UNITED STATES PATENTS 3,152,290 10/1964 Cassano et al 335/272 3,198,995 8/1965 Grebe 335/272 X FOREIGN PATENTS OR APPLICATIONS Great Britain 335/272 Primary ExaminerGeorge Harris Attorney-Robert E. Burns et a1.

[ 5 7 ABSTRACT A rotary electromagnetic actuator comprises a coil having a core extending diametrically of a cylindrical casing. Parallel pole pieces of arcuate cross section extending forwardly from opposite ends of the core receive between their forward ends a rotor mounted on a shaft extending axially of the casing. A spring tends to rotate the rotor in one direction while an electromagnetic force rotates it in the opposite direction when the coil is energized. Stop pins limit the angular movement of the rotor.

7 Claims, 3 Drawing Figures Patented July 3, 1973 FIG. 2

ROTARY ELECTROMAGNETIC ACTUATOR F CYLINDRICAL FORM The present invention relates to rotary electromagnetic actuators of the kind utilized for operating a signal or performing other useful work. In particular the invention relates to an actuator of small dimensions having, for example, a diameter of the order of 1 cm. and a length of 2 cm.

It is an object of the invention to provide a small, compact rotary electromagnetic actuator which is of simple construction, that is economical to manufacture and yet is effective and reliable in its operation. A further object of the invention is to provide a rotary electromagnetic actuator which is of cylindrical from in which the component parts are arranged to provide a compact construction so that an actuator having adequate power can be accommodated in a very small space.

The nature, object and advantages of the invention will be more fully understood from the following description of a preferred embodiment of the invention shown by way of example in the accompanying drawings in which:

FIG. 1 is a side view partially in axial section of a cylindrical electromagnetic actuator in accordance with the invention,

FIG. 2 is a cross section taken approximately on a line 22 in FIG. 1 and FIG. 3 is a cross section taken approximately on the line 3-3 in FIG. 1.

The preferred embodiment illustrated by way of example in the drawings is shown at a scale of approximately 10 to 1 in order that its construction may be seen more clearly.

The actuator shown in the drawings comprises an electromagnet 5 having a cylindrical winding 6 around a cylindrical core 7. The core is formed of soft iron or other suitable magnetic material and is electrically insulated from the winding, for example, by being wrapped with insulating tape. The winding is wound of insulated wire having self-bonding properties so that adjacent convolutions of the winding bond to one another and make the use of a coil form unnecessary. As seen in FIG. 1, opposite ends of the core project axially beyond the ends of the winding. The ends of the winding are suitably protected, for example, by tape or varnish or by nylon washers 8 as illustrated in the drawings. Suitable leads are provided for supplying current to the winding.

Two elongated pole pieces 10 fit over the projecting opposite end portions of the core 7 and extend parallel to one another in a direction perpendicular to the longitudinal axis of the core. The outer surfaces of the pole pieces are arcuate in cross section and are concentric with a line midway between the ends of the core 7 and perpendicular to the axis of the core. For convenience this line will herein be referred to as the longitudinal axis of the actuator. The inner surface of a rear portion 100 of each pole piece is flat and fits against the respective end of the winding 6, the respective end portion of the core 7 being received in a hole 11 in the pole piece. The inner surface of an intermediate portion 10b and a forward portion 10c of each pole piece are arcuate in cross section and concentric with the longitudinal axis of the actuator. The thickness of the forward portion 10c is reduced so as to provide a tapered shoulder 10d between the intermediate and forward portions. Moreover an inwardly projecting flange portion 10c is provided between the intermediate portion 10b and the rear portion 10a of the pole piece. The circumferential extent of each of the pole pieces is approximately The pole pieces are formed of soft iron or other suitable material having a high permeability.

A disc-shaped back plate 12 of suitable non-magnetic material, for example, brass, aluminum or plastic, is fitted between the intermediate portions 10b of the two pole pieces 10 and seated against the inwardly projecting flange portions we. The back plate 12 has a radius corresponding to the radius of the inner surface of the intermediate portions 1% of the pole pieces and hence fits between the pole pieces. It is suitable held in place, for example, by frinction or by adhesive. The back plate 12 is perpendicular to the longitudinal axis of the actuator.

A front housing 15 which is likewise formed of nonmagnetic material fits onto the front end portions of the pole pieces 10. The front housing 15 has a cylindrical wall 16 and an integral end wall 17. Th radius of the outer surface of the cylindrical wall 16 is at least approximately equal to the radius of the outer surfaces of the pole pieces and the radius of the inner surface of the cylindrical wall 16 is equal to or slightly larger than the radius of the inner surfaces of the pole pieces. The free end of the cylindrical wall 16, i.e., the end opposite the end wall 17, is provided with notches 16a which receive end portions of the pole pieces 10. The ends of the pole pieces fit snugly into the notches provided in the cylindrical wall of the front housing which is suitably secured in place, for example, by adhesive bonding of the front housing to the pole pieces. The electromagnet 5, pole pieces 10, back plate 12 and front housing 15 thus form a unitary structure. The end wall 17 of the front housing is perpendicular to the longitudinal axis of teh actuator.

A rotor 20 having a shaft 21 is rotatably mounted so as to rotate between the front end portions of the pole pieces 10. The shaft 21 is suitably mounted by low friction bearings to rotate about an axis that is coaxial with the longitudinal axis of the actuator. As shown by way of example in the drawings, the rear end of the shaft 21 is rotatably supported by a jewel bearing 22 set into a recess in the back plate 12. The rear end of the shaft is rounded or conical and butts an end stone 23 likewise set in a recess in the back plate. The shaft 21 extends forwardly through a hole in the center of the end wall 17 of the front housing and is rotatably supported by a jewel bearing 24 set in a recess in the end wall concentric with the hole. The forward end of the shaft 21 is provided with or'connected to the device that is to be actuated. For example, a flag (not shown) may be mounted on the forward end of the shaft. Forward movement of the shaft is limited by a shoulder on the shaft adapted to bear on the front jewel bearing 24. A shim 25 can be, if desired, provided between the shoulder and the bearing.

The rotor 20 comprises an approximately rectangular piece of soft iron or other suitable material of high permeability provided at its center with a hole through which the shaft 21 extends. The shaft 21 is formed of steel or other suitable material which has adequate strength, can be accurately machined and has a suitably low coefficient of friction with respect to the bearings. The rotor 20 is suitably fixed on the shaft 21, for example, by being a press fit or by adhesive, soldering or brazing. The ends of the rotor are rounded concentrically with the shaft and the rotor is of such length that when it is in position to extend diametrically between the opposite pole pieces, it approaches the pole pieces as closely as possible without frictional engagement. Hence with the rotor in this position the rotor together with the pole pieces and the core 7 form a substantially closed magnetic circuit for the electromagnetic 5.

It will be understood that when the electromagnetic is energized, magnetic forces tend to pull the rotor 20 into a position in which it extends across between the forward end portions of the pole pieces. Spring means is provided for biasing the rotor to a rest position in which it does not extend across between the pole pieces. Such biasing means is shown by way of example in the drawings as a spirally coiled hair spring 27 which surrounds the rotor shaft2l. The inner end of the hair spring is secured to a split hub 28 which is mounted on the shaft 21 forwardly of the rotor 20. The outer end of the hair spring is provided with a hook which hooks into a counter sunk hole 30 in the cylindrical wall 16 of the front housing 15 and preferably secured in place, for example, by adhesive. The spiral spring is tensioned so that it tends to rotate the shaft 21 to turn the rotor 20 to a rest position.

The actuator is provided with suitable means for limiting rotation of the rotor to define rest and actuated positions of the rotor. Such limiting means is conveniently providdd in the form of one or more stop pins engageable by the rotor. By way of example in the drawings there is shown a stop pin 31 set in a hole in one of the pole pieces to limit rotation of the rotor in its activated position and a second stop pin 32 set in a hole in the cylindrical wall of the front housing to limit rotation of the rotor in its rest position. The end portions of the stop pins are preferably bevelled as shown to conform to the edge surface of the rotor and thereby provide a larger bearing surface. It will be understood that the location of the stop pins is selected to define the positions of the rotor as desired. For convenience of manufacture both pole pieces are provided with holes for receiving stop pins where the stop pin is mounted on only one pole piece,the hole provided in the other pole piece being filled with a plug 33 of magnetic material.

A cylindrical cover 35 of suitable non-magnetic material, for example, aluminum, encloses the entire assembly of electromagnet, pole pieces, back plate, front housing and rotor. The cover is shown as comprising a cylindrical wall 36 and an end wall 37. The cylindrical wall as fits snugly over the pole pieces l0 and the cylindrical wall 16 of the front housing 115 and extends to the front face of the front housing. The end wall 117 of the front housing and the end wall 37 of the cover provide end closures for the actuator. A cylindrical projection or boss 38 of smaller diameter than the circular wall 36 extends rearwardly from the end wall 37 of the cover 35 and provides means for conveniently mounting the actuator on a suitable support. The boss 38 is preferably provided with a central tapped hole to receive a screw or bolt for securing the actuator to the supporting structure.

The operation of the actuator will be readily understood from the foregoing description. When the elctromagnet 5 is not energized, the rotor is held in rest position against the stop 32 by the hair spring 27. When the electromagnet 5 is energized, the magnetic forces acting on the rotor tend to turn it to a position in which the rotor extends across between the opposite pole pieces. MQvement of the magnetic actuator is limited by the stop 31 which defines the actuated position of the rotor. With the location of the stop pin 31 as shown in the drawings movement of the rotor by the electromagnet is stopped before the rotor reaches a position in which it extends straight across between the opposite pole pieces. Hence in this position there is still an electromagnetic force tending to turn the rotor farther and thereby holding it firmly against the stop pin 31 as long as the electromagnet is energized. When the magnet is de-energized, the rotor is reutrned to its rest position by the hair spring 27.

It will be seen that the construction in accordance with the present invention provides a simple and compact rotary electromagnetic actuator which occupies a very small space and yet provides effective and efficient operation.

While a preferred embodiment of a rotary electromagnetic actuator in accordance with the present invention has been illustrated in the drawings and is herein particularly described, it will be understood that the invention is in no way limited to the details of construction of the illustrated embodiment.

What I claim and desire to secure by letters patent is:

l. A cylindrical rotary electromagnetic actuator comprising an electromagnet having an annular winding and a core of ferromagnetic material extending axially through said winding, two pole pieces of ferromag netic material extending respectively from opposite ends of said winding and core in a direction perpendicular to the axis of said winding and parallel to one another, said pole pieces having diametrically opposite forward portions of arcuate cross sectional shape, a back plate of non-magnetic material extending between intermediate portions of said pole pieces and disposed in a plane normal to said pole pieces, a front housing of non-magnetic material having a front plate parallel to said back plate and integral cylindrical portions notched to receive the arcuate forward portions of said pole pieces, said cylindrical portions of said front housing and said pole pieces together constituting a cylindrical wall, a shaft coaxial with said cylindrical wall extending forwardly from said back plate and out through a central opening in said front plate, bearing means in said back plate and said front plate rotatably supporting said shaft, a rotor fixed on said shaft and comprising a bar of ferromagnetic material extending transversely of aid shaft and of a length to extend substantially to but clear arcuate forward end portions of said pole pieces, means for limiting rotary movement of said rotor between a first position in which said bar ex tends between said pole pieces and a second position at a selected angle to said first position,and means biasing said rotor to said second position, said winding being energizable to produce a magnetic field for moving said rotor from said second position to said first position by electromagnetic force overcoming the force of said biasing means.

2. A rotary electromagnetic actuator according to claim ll, in which said bearing means in said back plate comprises a thrust bearing engaging the rear end of said shaft and a radial jewel bearing.

3. A rotary electromagnetic actuator according to claim l, in which said .means for limiting rotation of said rotor comprises a stop pin extending inwardly from said cylindrical wall and engageable by said rotor.

4. A rotary electromagnetic actuator according to claim 1, further comprising a cylindrical cover of nonmagnetic material snugly receiving the assembly comprising said electromagnet, pole pieces and front housmg.

5. A rotary electromagnetic actuator according to claim 1, in which said biasing means comprises a spiral spring having one end secured to said shaft and another end secured to said cylindrical wall.

6. A rotary electromagnetic actuator comprising an electromagnetic having an annular winding and a core of ferromagnetic material extending axially through said winding, two pole pieces of ferromagnetic material extending respectively from opposite ends of said winding and core in a direction perpendicular to the axis of said winding and parallel to one another, said pole pieces having foward portions of arcuate cross sectional shape, means including said pole pieces defining a chamber with a cylindrical wall and a front end wall perpendicular to said pole pieces, a shaft disposed in said chamber and extending out through an opening in said end wall, bearing means rotatably supporting said shaft coaxial with said arcuate portions of said pole pieces, a rotor fixed on said shaft and comprising a bar of ferromagnetic material extending transversely of said shaft and of a length to extend substantially to but clear said arcuate portions of said pole pieces, means for limiting rotary movement of said rotor between a first position in which said barextends between said pole pieces and a second position at a selected angle to said first position, and means for biasing said rotor to said second position, said winding being energizable to produce a magnetic field for moving said rotor from said second position to said first position by electromagnetic force overcoming the force of said biasing means, said limiting means comprising a pin extending through a hole in said cylindrical wall and projecting inwardly of said wall in position to be engaged by said rotor.

7. A rotary electromagnetic actuator according to claim 6, in which the inner end of said pin has an inclined surface engageable by said rotor. 

1. A cylindrical rotary electromagnetic actuator comprising an electromagnet having an annular winding and a core of ferromagnetic material extending axially through said winding, two pole pieces of ferromagnetic material extending respectively from opposite ends of said winding and core in a direction perpendicular to the axis of said winding and parallel to one another, said pole pieces having diametrically opposite forward portions of arcuate cross sectional shape, a back plate of nonmagnetic material extending between intermediate portions of said pole pieces and disposed in a plane normal to said pole pieces, a front housing of non-magnetic material having a front plate parallel to said back plate and integral cylindrical portions notched to receive the arcuate forward portions of said pole pieces, said cylindrical portions of said front housing and said pole pieces together constituting a cylindrical wall, a shaft coaxial with said cylindrical wall extending forwardly from said back plate and out through a central opening in said front plate, bearing means in said back plate and said front plate rotatably supporting said shaft, a rotor fixed on said shaft and comprising a bar of ferromagnetic material extending transversely of said shaft and of a length to extend substantially to but clear arcuate forward end portions of said pole pieces, means for limiting rotary movement of said rotor between a first position in which said bar extends between said pole pieces and a second position at a selected angle to said first position, and means biasing said rotor to said second position, said winding being energizable to produce a magnetic field for moving said rotor from said second position to said first position by electromagnetic force overcoming the force of said biasing means.
 2. A rotary electromagnetic actuator according to claim 1, in which said bearing means in said back plate comprises a thrust bearing engaging the rear end of said shaft and a radial jewel bearing.
 3. A rotary electromagnetic actuator according to claim 1, in which said means for limiting rotation of said rotor comprises a stop pin extending inwardly from said cylindrical wall and engageable by said rotor.
 4. A rotary electromagnetic actuator according to claim 1, further comprising a cylindrical cover of non-magnetic material snugly receiving the assembly comprising said electromagnet, pole pieces and front housing.
 5. A rotary electromagnetic actuator according to claim 1, in which said biasing means comprises a spiral spring having one end secured to said shaft and another end secured to said cylindrical wall.
 6. A rotary electromagnetic actuator comprising an electromagnetic having an annular winding and a core of ferromagnetic material extending axially through said winding, two pole pieces of ferromagnetic material extending respectively from opposite ends of said winding and core in a direction perpendicular to the axis of said winding and parallel to one another, said pole pieces having foward portions of arcuate cross sectional shape, means including said pole pieces defining a chamber with a cylindrical wall and a front end wall perpendicular to said pole pieces, a shaft disposed in said chamber and extending out through an opening in said end wall, bearing means rotatably supporting said shaft coaxial with said arcuate portions of said pole pieces, a rotor fixed on said shaft and comprising a bar of ferromagnetic material extending transversely of said shaft and of a length to extend substantially to but clear said arcuate portions of said pole pieces, means for limiting rotary movement of said rotor between a first position in which said bar extends between said pole pieces and a second position at a selected angle to said first position, and means for biasing said rotor to said second position, said winding being energizable to produce a magnetic field for moving said rotor from said second position to said first position by electromagnetic force overcoming the force of said biasing means, said limiting means comprising a pin extending through a hole in said cylindrical wall and projecting inwardly of said wall in position to be engaged by said rotor.
 7. A rotary electromagnetic actuator according to claim 6, in which the inner end of said pin has an inclined surface engageable by said rotor. 